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US5450623A - CN ratio measuring apparatus - Google Patents

CN ratio measuring apparatus Download PDF

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Publication number
US5450623A
US5450623A US08122281 US12228193A US5450623A US 5450623 A US5450623 A US 5450623A US 08122281 US08122281 US 08122281 US 12228193 A US12228193 A US 12228193A US 5450623 A US5450623 A US 5450623A
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frequency
level
measuring
ratio
noise
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Expired - Lifetime
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US08122281
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Itoshi Yokoyama
Masaaki Nagai
Kenichi Ishida
Kakuya Saito
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Leader Electronics Corp
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Leader Electronics Corp
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B17/00Monitoring; Testing
    • H04B17/20Monitoring; Testing of receivers

Abstract

A measuring apparatus is provided which is capable of measuring CN ratio. The measuring apparatus has a measuring band specifying unit for specifying a band under measurement; a display for displaying the spectrum of levels measured in the specified band; first and second noise measuring frequency specifying units; a transmission channel selector; and a CN ratio calculating unit for estimating a noise level at a carrier of a selected transmission channel and for calculating the CN ratio using the estimated level.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a CN (Carrier to Noise) ratio measuring apparatus for measuring the CN ratio of signals sent along transmission paths such as a transmission path of a broadcast satellite or a communication satellite.

2. Description of the Prior Art

Conventionally, there are known three types of methods of measuring CN ratio (ratio of a carrier power to a noise power) for satellite broadcast signals. A first type is known as "an in-carrier noise equalizing method" which is disclosed in Japanese Patent Public-Disclosure No. 61-274495. The method is employed for detecting a noise power in a vertical blanking period of a TV video signal and calculates the ratio of the noise power to a separately measured carrier power to derive a CN ratio. A second type is known as "an SN ratio converting method" which demodulates a received signal and measures the SN ratio for the demodulated signal which is then converted to a CN ratio. A third type is a method using a spectrum analyzer. "New CATV Techniques" edited by Electric Telecommunication Technology Committee describes on pages 246-257 "CN Ratio Measuring Method for Signals Received through Satellite Broadcasting" using a spectrum analyzer. This method measures the electric power of noise immediately outside of the band of a carrier to be measured to derive a noise power of the carrier and calculate the ratio of the thus measured noise power to a separately measured power of the carrier.

Since the in-carrier noise equalizing method extracts noise in the vertical blanking period, it requires the use of a complicated demodulator. The second SN ratio converting method also requires a demodulator which must be stable over a wide band. Further, the third method using a spectrum analyzer not only requires an expensive spectrum analyzer but also is required to perform complicated calculations for deriving a CN ratio.

SUMMARY OF THE INVENTION

In view of the problems stated above, it is an object of the present invention to provide a CN ratio measuring apparatus which allows an operator to easily measure a CN ratio.

It is another object of the present invention to provide a low cost CN ratio measuring apparatus which is capable of measuring a CN ratio.

To achieve the above objects, the present invention utilizes the fact that a noise level of a carrier on at least one transmission channel is substantially linear in a frequency band including the frequency of the carrier on a logarithmic frequency scale.

Specifically, a CN ratio measuring apparatus according to the present invention is adapted to measure the CN ratio of a signal transmitted through at least one transmission channel included in a transmission path, and comprises level measuring means having an input for receiving an output of the transmission path, a frequency specifying input for receiving signals which specify frequencies, an output for generating levels measured at frequencies specified by the signals received by the frequency specifying input; means for generating to the frequency specifying input a signal which specifies a frequency band in which the output of the transmission path is to be measured; display means coupled to the output of the level measuring means for displaying the spectrum of the measured levels in the frequency band under measurement; transmission channel selecting means coupled to the frequency specifying input for specifying a first frequency which is a carrier frequency of a selected one in the at least one transmission channel; noise measuring frequency specifying means coupled to the frequency specifying input for specifying a second frequency which is lower than the carrier frequency of the selected transmission channel and at which no signal components are present, and a third frequency which is higher than the carrier frequency of the selected transmission channel and at which no signal components are present; and CN ratio calculating means coupled to an output of the transmission channel selecting means, an output of the noise measuring frequency specifying means and the output of the level measuring means for deriving a CN ratio of the selected transmission channel from the first, second and third frequencies and first, second and third measured levels at the respective frequencies generated from the level measuring means.

Also, according to the present invention, the CN ratio calculating means includes means for deriving a fourth level, which is a noise level at the first frequency, from the second and third measured levels, as well as the first, second and third frequencies; and means for deriving the CN ratio from the first measured level and the fourth level.

Further, according to the present invention, the second and third frequencies are specified to values which are regarded to exhibit a noise level linearity between the second and third frequencies with respect to frequency, in accordance with the spectrum of measured levels displayed on the display means.

Further, according to the present invention, the at least one transmission channel includes a plurality of channels, the second frequency is specified to be a value lower than the lowest frequency channel of the plurality of channels, and the third frequency is specified to be a value higher than the highest frequency channel of the plurality of channels.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be explained in connection with the preferred embodiment with reference to the accompanying drawings:

FIG. 1 is a diagram illustrating a basic configuration of a CN ratio measuring apparatus according to the present invention;

FIG. 2 is a frequency spectrum diagram used for explaining a method of estimating a noise level of a carrier in a transmission channel;

FIG. 3 is a block diagram illustrating a circuit of a TV/SAT signal level meter AA which embodies the basic configuration of FIG. 1;

FIG. 4 is a view illustrating a front panel of the signal level meter shown in FIG. 3;

FIG. 5 is a flowchart illustrating a procedure of the CN ratio measurement executed by a CPU shown in FIG. 3;

FIGS. 6(a)-6(c) are diagrams illustrating images displayed on the screen of FIG. 4 during executing the CN ratio measuring flow;

FIGS. 7(a)-7(c) are diagrams illustrating displays presented on the screen of FIG. 4 during executing the CN ratio measuring flow;

FIGS. 8(a)-8(c) are diagrams illustrating displays presented on the screen of FIG. 4 during executing the CN ratio measuring flow;

FIGS. 9(a) and 9(b) are diagrams illustrating displays for displaying a measured CN ratio on the screen; and

FIG. 9(c) illustrates a printed data list for all specified channels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT:

FIG. 1 illustrates a basic configuration of a CN ratio measuring apparatus A according to the present invention. The measuring apparatus A is capable of measuring the CN ratio of a signal on a transmission path having at least one transmission channel. As can be seen from the drawing, the apparatus A has an input terminal 1 for receiving an output from the transmission path. The input terminal 1 is coupled to a level measuring unit 2 which has a plurality of frequency specifying inputs a, b, c and d each for receiving a signal for specifying a frequency or frequencies at which level measurement is performed; and an output for providing measured levels at frequencies specified by the signals received at the frequency specifying inputs. A measured band specifying unit 3 is provided for generating a signal for specifying a frequency band in which an output of the transmission path is to be measured. The frequency band specifying signal is provided to the frequency specifying input a. The output of the level measuring unit 2 is coupled to a display unit 4 which displays the spectrum of levels measured in the measured frequency band. A transmission channel selector 5 is coupled to the frequency specifying input d for specifying the carrier frequency of a transmission channel selected within at least one transmission channels. First and second noise measuring frequency specifying units 6 and 7 are respectively coupled to the frequency specifying input terminals b and c for specifying a first noise measuring frequency N1 which is lower than the carrier frequency of the selected transmission channel and at which no signal components are present, and a second noise measuring frequency N2 which is higher than the selected transmission channel carrier frequency and at which no signal components are present. Further, the CN ratio measuring apparatus A comprises a CN ratio calculating unit 8 which is coupled to the outputs of the selector 5, specifying units 6 and 7, and level measuring unit 2. The output of the calculating unit 8 is coupled to the display unit 4.

The measuring apparatus A operates in two modes. In a first operation mode, the level measuring unit 2 sequentially measures levels in every predetermined frequency band over a frequency region under measurement and displays the spectrum on the display unit 4. In a second operation mode, when the frequencies N1 and N2 and the carrier frequency are specified, the level measuring unit 2 sequentially measures levels at each of the frequencies and outputs measured level values to the calculating unit 8. The calculating unit 8 calculates the CN ratio of the selected transmission channel from the frequencies and the respective measured level values corresponding thereto, and feeds the calculation result to the display unit 4 for display.

Now, the principle of the CN ratio calculation performed by the calculating unit 8 will be explained with reference to FIG. 2. The calculating method is similar to the CN ratio measurement by the conventional method using a spectrum analyzer. FIG. 2 illustrates a frequency spectrum of a frequency band including three transmission channels which includes noise components n, the level of which decreases as the frequency is higher, and three carrier components c1, c2 and c3. Note that the vertical axis in FIG. 2 represents levels in dBμV. As illustrated, when the level of the noise components n varies in a substantially linear relationship with the frequency, a noise level LNfc1 of the carrier c1 can be estimated from noise levels LN1 and LN2 at the frequencies N1 and N2 which are outside of the carrier band and the ratio of (fc1 -N1) to (N2-N1). The accuracy of the estimation becomes higher as the degree of linearity of the noise components n increases and N1 and N2 are set closer to the carrier frequency fc1.

For example, in a BS channel, signals from a broadcasting satellite are received by a parabolic antenna, amplified by a converter attached to the antenna, and coupled to a BS tuner through a cable. Generally, the converter is designed such that the frequency characteristics thereof is substantially flat. The cable causes signals to be attenuated due to cable loss in logarithmically linear fashion. Therefore, in most cases, the level of noise appearing at the output of the convertor or at the input of the BS tuner presents substantially flat or logarithmically linear attenuation. Thus, the noise level of a carrier can be approximately calculated by the aforementioned method.

Once an estimated value of the noise level LNfc1 of the carrier cl is derived, the CN ratio can be calculated by measuring the level Lfc1 of the carrier cl. While explanation has been given of the calculation of the CN ratio for the carrier cl, the CN ratio can be calculated in a similar manner for the other carriers c2 and c3. When the carrier c1 is the only one in the spectrum shown in FIG. 2, a value more approximate to the noise level LNfc1 can be derived if N2 is brought closer to fc1.

Next, a TV/SAT (satellite) signal level meter AA which embodies the basic configuration of the present invention will be explained with reference to FIGS. 3 and 4. It should be noted that since TV signal level measurement is not related to the present invention, explanation thereof will be omitted, and parts associated with the SAT signal will only be explained.

As shown in FIG. 3, the meter AA comprises a radio frequency attenuator 20 coupled to an input terminal 10 (providing attenuation ranging 0-60 dB with steps of 10 dB); a BS/CS tuner 22 (for example, having a bandwidth of 24 MHz) coupled to the output of the attenuator 20; and a direct current amplifier 24 for amplifying a detection output of the tuner 22. The meter AA also comprises a CPU 90 and a variety of elements associated therewith, i.e., a liquid crystal display (LCD) unit 40 (having for example, 128×160 dots); a RAM 92 (for storing part of software); an EPROM 94 (for storing software); an EEPROM 96 (for storing data); and a group of keys 98. The CPU 90 outputs a signal for specifying an attenuation ratio to the attenuator 20 on a line 100, as well as frequencies to be tuned, i.e., the frequencies N1 and N2 and the carrier frequency (fc), to the tuner 22 on a line 102. Further, the CPU 90 receives a detection output obtained with a specified attenuation ratio in a specified frequency band from the amplifier 24 through a line 104 at an ADC incorporated in the CPU.

FIG. 4 illustrates a front panel of the meter AA. As can be seen from the drawing, the front panel has a display screen 400 and an operation panel 402. While the display screen 400 is capable of presenting displays in a variety of patterns, the illustrated screen presents a region 403 for displaying information on a channel (channel number, frequency, measured level, CN ratio and so on); a spectrum display region 404 for displaying the frequency spectrum of a band under measurement in a bar-graph form; and a region 406 for displaying noise measuring frequencies. The operation panel 402 includes a measuring key group, an editing (EDIT) key group, and another key group. The measuring key group includes a TV/SAT selection key, a program recall (PRG RECALL) key, and an up/down key for PRG/CHANNEL. The editing key group includes an item selection (ITEM) key, a position selection (POSITION) key, and a character selection (CHARACTER) key.

Next, the operation of the meter AA will be explained with reference to a flowchart of FIG. 5 showing a procedure of the CN ratio measurement and examples of displayed images on the screen shown in FIGS. 6-9. It should be noted that the operation of the meter AA is divided into a level measurement/display mode and a CN ratio measurement/display mode.

First, entering the level measurement/display mode, a band subjected to level measurement is first inputted at step 900. Next, at step 902, measured levels in the band under measurement are displayed in a spectrum form as shown in FIG. 4 (selected channel and N1 and N2 displayed in FIG. 4 are those which have previously been set).

Next, after entering the CN ratio measurement/display mode, a CN ratio measurement process is started at step 904, where the noise measuring frequencies N1 and N2 and one or more carrier frequencies fci (i=1,2,3, . . . ) are inputted. More specifically, the PRG EDIT key is depressed to cause <SAT> PRG EDT screen to appear (FIG. 6(a)). Now, each channel at which the CN ratio is to be measured is set (in FIG. 6(a), four BS channels 5, 7, 9 and 11 have been set). Next, the ITEM key is depressed to invert in intensity the display region showing the C/N setting which is now indicating "OFF" (FIG. 6(b)). Next, the CHARACTER key is depressed to switch the C/N setting from "OFF" to "ON". Thus, a screen for setting noise measuring frequencies is displayed (FIG. 6(c)).

Next, the ITEM key is depressed to invert in intensity the display of the noise measuring frequency N1 in a lower portion of the screen (FIG. 7(a)). At this time, an inverted black triangle () is moved to a cursor indicating N1 on a displayed bar graph, and an initially set value of the frequency N1 is displayed in a region under the bar graph (N1 =1010 MHz). Next, the PRG/CHARACTER key is depressed to set the frequency N1 to a desired frequency which is lower than the lowest carrier frequency of all and close to the carrier frequency (preferably, separated by approximately 40 MHz), i.e., 1,080 MHz in this example (FIG. 7(b)). In this example, the noise measuring frequency can be set in a range from 950 to 1,600 MHz with steps of 10 MHz.

Next, the ITEM key is depressed to invert in intensity the display indicating the noise measuring frequency N2. At this time, the inverted black triangle () is moved to a cursor indicating N2 on the displayed bar graph, and an initially set value of N2 is displayed as N2=1360 MHz (FIG. 7(c)). Subsequently, the PRG/CHARACTER key is used to set the frequency N2 to a desired frequency which is higher than the highest carrier frequency and close to the carrier frequency (preferably separated by approximately 40 MHz), i.e., 1,280 MHz in this example (FIG. 8(a)). Thereafter, the PRG EDIT key is depressed to return to the <SAT> PRG EDIT screen (FIG. 8(b)). Then, the C/N setting is displayed as being "ON" for the BS channels 5, 7, 9 and 11, and the frequencies N1 and N2 set at values by the foregoing procedure are displayed on the screen. When all the setting has been completed for the channels, the contents of the setting can be programmed as shown in FIG. 8(c).

Next, at step 906, a noise level LN1 (in dBμV) is measured at the frequency N1. For this purpose, the CPU 90 supplies the tuner 22 with a signal for tuning the same at the frequency N1 and the attenuator 22 with a signal for specifying an appropriate attenuation ratio, and receives, as a result, a DC level value from the amplifier 24. The DC level value is used to calculate a received level together with the specified attenuation ratio. Further, the received level is subjected to a level compensation with respect to an average detection of noise of the tuner 22 (the compensation is performed because the relation between the input level and DC output level of the amplifier 24 is deviated between noise and carrier), and a band conversion (from 24 MHz to 27 MHz) is performed to derive a measured noise level LN1. Likewise, at step 908, a measured noise level LN2 (in dBμV) is derived for the frequency N2.

Next, at step 910, the carrier frequency fc is set to fc1 (the frequency of the BS channel 5, in this example), and a noise level LNfc (in dBμV) of the carrier frequency is calculated according to the following equation:

L.sub.Nfc =[{(f.sub.c -N1)/(N2-N1)}(L.sub.N1 -L.sub.N2)]+L.sub.N1

This is the method explained in connection with FIG. 2 which calculates the noise level by linear approximation. Next, at step 914, a level Lfc of the carrier is measured. This is performed also in a method similar to that explained at step 906. However, performed this time is a compensation with respect to the average detection of a carrier. Subsequently, at step 916, the CN ratio for the channel is calculated by the following equation, and the calculation result is displayed.

CN ratio=L.sub.fc -L.sub.Nfc

Next, at step 918, it is determined whether the CN ratios have been measured for all the channels. If NO, the steps 910-916 are repeated for a next channel (the BS channel 7 in this example), and this flow is terminated when the answer to the determination at step 918 is YES.

FIGS. 9(a) and 9(b) illustrate examples of available screens after the CN ratios have been measured for all the specified BS channels 5, 7, 9 and 11. More specifically, FIG. 9(a) illustrates a screen which displays a bar graph representation of the respective levels of all the channels and information on a channel indicated by a cursor (i.e., channel 5), and FIG. 9(b) illustrates a screen which displays only one of all the channels (channel 5 in this example) in greater detail. FIG. 9(c) in turn shows a printed list of data on all the specified channels.

One embodiment of the present invention has been explained in connection with BS channels. As will be understood, the present invention can also be applied to other transmission channels such as communication satellite (CS) channels, wired and wireless TV transmission channels, micro-wave cables, and so on. Also, the frequencies N1 and N2 may be set by inputting numerical values instead of manipulating the PRG/CHARACTER key.

According to the present invention as described above, since a common level measuring circuit can be used for measuring noise levels and carrier levels, the measuring apparatus can be manufactured at a lower cost. Also, since the user is freed from the necessity of making complicated calculations, the measurement can be easily made. Further, the present invention is advantageous in that the CN ratio measurement can be achieved even if modulating waves such as video signals are different.

Claims (9)

What is claimed is:
1. A carrier-to-noise (CN) ratio measuring apparatus for measuring a CN ratio of a signal transmitted through at least one transmission channel included in a transmission path, comprising:
level measuring means having an input for receiving an output of said transmission path, a frequency specifying input for receiving signals which specify frequencies, an output for generating levels measured at frequencies specified by the signals received by said frequency specifying input;
means for generating to said frequency specifying input a signal which specifies a frequency band in which the output of said transmission path is to be measured;
display means coupled to the output of said level measuring means for displaying a spectrum of said measured levels in said frequency band under measurement;
transmission channel selecting means coupled to said frequency specifying input for specifying a first frequency which is a carrier frequency of a selected one in said at least one transmission channel, said carrier frequency of said selected transmission channel being within said frequency band under measurement;
noise measuring frequency specifying means coupled to said frequency specifying input for specifying a second frequency which is lower than the carrier frequency of said selected transmission channel and at which no signal components are present, and a third frequency which is higher than the carrier frequency of said selected transmission channel and at which no signal components are present, said second and third frequencies being also within said frequency band under measurement, said second and third frequencies being capable of being varied by an operator; and
CN ratio calculating means coupled to an output of said transmission channel selecting means, an output of said noise measuring frequency specifying-means and the output of said level measuring means for deriving said CN ratio of said selected transmission channel from said first, second and third frequencies and first, second and third measured levels, said first, second and third measured levels being derived from the output of said level measuring means when respective signals specifying said respective first, second and third frequencies are applied to the frequency specifying input of said level measuring means, said CN ratio calculating means including:
1. means for deriving a fourth level, which is a noise level at said first frequency, from said second and third measured levels and said first, second and third frequencies by determining the fourth level at said first frequency from the second measured level at said second frequency and the third measured level at said third frequency by linear approximation; and
2. means for deriving said CN ratio from said first measured level and said fourth level.
2. A carrier-to-noise ratio measuring apparatus according to claim 1, wherein said second and third frequencies are specified to values which are regarded to exhibit a noise level linearity between the second and third frequencies with respect to frequency, in accordance with the spectrum of measured levels displayed on said display means.
3. A carrier-to-noise ration measuring apparatus according to claim 1, wherein said at least one transmission channel includes a plurality of channels, said second frequency is specified to be a value lower than the lowest frequency channel of said plurality of channels, and said third frequency is specified to be a value higher than the highest frequency channel of said plurality of channels.
4. A carrier-to-noise ratio measuring apparatus according to any one of claims 1, 2 and 3, wherein an output of said CN ratio calculating means is coupled to said display means for displaying said CN ratio on said display means.
5. A carrier-to-noise ratio measuring apparatus according to any one of claims 1, 2 and 3, wherein said level measuring means includes a radio frequency attenuator having an input and an output, a tuner having an input connected to the output of the attenuator and an output, and a direct current amplifier having an input connected to the output of the tuner and an output.
6. A carrier-to-noise (CN) ratio measuring apparatus for measuring a CN ratio of a signal transmitted through at least one transmission channel included in a transmission path and for deriving a noise power on a selected transmission channel comprising:
level measuring means having an input for receiving an output from said transmission path, a frequency specifying input for receiving signals for specifying frequencies, an output for generating levels measured in every predetermined frequency band at frequencies specified by the signals received by said frequency specifying input:
means for generating to said frequency specifying input, a signal which specifies a frequency band in which the output of said transmission path is to be measured:
display means coupled to the output of said level measuring means for displaying the spectrum of said measured levels in said frequency band under measurement;
transmission channel selecting means coupled to said frequency specifying input for specifying a first frequency which is a carrier frequency of said selected transmission channel, paid carrier frequency of said selected transmission channel being within said frequency band under measurement;
noise measuring frequency specifying means coupled to said frequency specifying input for specifying in accordance with the spectrum of said measured levels displayed a second frequency which is lower than the carrier frequency of said selected transmission channel and at which no signal components are present, and a third frequency which is higher than the carrier frequency of said selected transmission channel and at which no signal components are present, said second and third frequencies being also within said frequency band under measurement, said second and third frequencies being capable of being varied by an operator; and
means coupled to an output of said transmission channel selecting means, an output of said noise measuring frequency specifying means and the output of said level measuring means for deriving said noise power of said selected transmission channel from said first, second and third frequencies and first and second measured levels, said first and second measured levels being derived from the output of said level measuring,means when respective signals specifying said respective second and third frequencies are applied to the frequency specifying input of said level measuring means, said means for deriving said noise power including:
means for deriving a third level, which is a noise level at said first frequency, from said first and second measured levels and said first, second and third frequencies by determining the third level at said first frequency from the first measured level at said second frequency and the second measured level at said third frequency by linear approximation.
7. A carrier-to-noise ratio measuring apparatus according to claim 6, wherein said second and third frequencies are specified to values which are regarded to exhibit a noise level linearity between the second and third frequencies with respect to frequency, in accordance with the spectrum of measured levels displayed on said display means.
8. A carrier-to-noise ratio measuring apparatus according to claim 6, wherein said at least one transmission channel includes a plurality of channels, said second frequency is specified to be a value lower than the lowest frequency channel of said plurality of channels, and said third frequency is specified to be a value higher than the highest frequency channel of said plurality of channels.
US08122281 1992-09-18 1993-09-17 CN ratio measuring apparatus Expired - Lifetime US5450623A (en)

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JP25001792A JP3135999B2 (en) 1992-09-18 1992-09-18 Cn ratio measurement device

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Cited By (38)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5802446A (en) * 1995-03-08 1998-09-01 U.S. Philips Corporation Method and apparatus for testing a communication channel
US5825817A (en) * 1994-07-22 1998-10-20 Anritsu Corporation Radio wave measuring apparatus for digital communication system
US5924023A (en) * 1995-12-21 1999-07-13 Anthony J. Smith Channel operation monitoring in cellular communications networks
US5950110A (en) * 1997-08-06 1999-09-07 Interactive Techanologies, Inc. Jamming detection in a wireless security system
US6021159A (en) * 1997-05-28 2000-02-01 Ikegami Tsushinki Co., Ltd. Circuit for measuring transmission quality of demodulated digital signal transmitted under carrier modulation transmission system
WO2000019643A1 (en) * 1998-09-28 2000-04-06 Motorola Inc. A terminal unit and a method for locating a terminal unit
US6131014A (en) * 1998-03-17 2000-10-10 Fujitsu Limited Bidirectional communication system and upstream communication noise level determination method
US6330432B1 (en) * 1998-02-25 2001-12-11 Nortel Networks Limited Determining SIR in a communications system
US6330431B1 (en) * 1997-07-08 2001-12-11 Telefonaktiebolaget Lm Ericsson (Publ) Method and apparatus for measuring signal quality in a wireless communication system
US6397041B1 (en) * 1999-12-22 2002-05-28 Radio Propagation Services, Inc. Broadcast monitoring and control system
US20040005858A1 (en) * 2002-07-03 2004-01-08 Alexandre Cervinka Detector of commercial jammer
US20040136469A1 (en) * 2001-04-27 2004-07-15 Weizheng Wang Optimization technique for layered modulation
US20040184521A1 (en) * 2001-04-27 2004-09-23 Chen Ernest C. Equalizers for layered modulated and other signals
US20040203427A1 (en) * 2002-08-19 2004-10-14 Hill Thomas C. Remote estimation of amplifier functionality
US20050036450A1 (en) * 2003-06-16 2005-02-17 Kozue Arimori Network monitoring system, reproduction terminal, and monitoring terminal
US6985737B2 (en) * 2001-08-28 2006-01-10 Ntt Docomo, Inc. Communication channel setting method, communication controller, and radio communication system
US20060013333A1 (en) * 2001-04-27 2006-01-19 The Directv Group, Inc. Maximizing power and spectral efficiencies for layered and conventional modulations
US20060056541A1 (en) * 2002-07-01 2006-03-16 Chen Ernest C Improving hierarchical 8psk performance
US20060153314A1 (en) * 2002-10-25 2006-07-13 Chen Ernest C Method and apparatus for tailoring carrier power requirements according to availability in layered modulation systems
US7151807B2 (en) 2001-04-27 2006-12-19 The Directv Group, Inc. Fast acquisition of timing and carrier frequency from received signal
US7173981B1 (en) 2001-04-27 2007-02-06 The Directv Group, Inc. Dual layer signal processing in a layered modulation digital signal system
US7209524B2 (en) 2001-04-27 2007-04-24 The Directv Group, Inc. Layered modulation for digital signals
US7230480B2 (en) 2002-10-25 2007-06-12 The Directv Group, Inc. Estimating the operating point on a non-linear traveling wave tube amplifier
US7245671B1 (en) 2001-04-27 2007-07-17 The Directv Group, Inc. Preprocessing signal layers in a layered modulation digital signal system to use legacy receivers
US7423987B2 (en) 2001-04-27 2008-09-09 The Directv Group, Inc. Feeder link configurations to support layered modulation for digital signals
US7463676B2 (en) 2002-10-25 2008-12-09 The Directv Group, Inc. On-line phase noise measurement for layered modulation
US7474710B2 (en) 2002-10-25 2009-01-06 The Directv Group, Inc. Amplitude and phase matching for layered modulation reception
US7483505B2 (en) 2001-04-27 2009-01-27 The Directv Group, Inc. Unblind equalizer architecture for digital communication systems
US7502429B2 (en) 2003-10-10 2009-03-10 The Directv Group, Inc. Equalization for traveling wave tube amplifier nonlinearity measurements
US7502430B2 (en) 2001-04-27 2009-03-10 The Directv Group, Inc. Coherent averaging for measuring traveling wave tube amplifier nonlinearity
US7512189B2 (en) 2001-04-27 2009-03-31 The Directv Group, Inc. Lower complexity layered modulation signal processor
US7529312B2 (en) 2002-10-25 2009-05-05 The Directv Group, Inc. Layered modulation for terrestrial ATSC applications
US7583728B2 (en) 2002-10-25 2009-09-01 The Directv Group, Inc. Equalizers for layered modulated and other signals
US7639759B2 (en) 2001-04-27 2009-12-29 The Directv Group, Inc. Carrier to noise ratio estimations from a received signal
US7738587B2 (en) 2002-07-03 2010-06-15 The Directv Group, Inc. Method and apparatus for layered modulation
US7778365B2 (en) 2001-04-27 2010-08-17 The Directv Group, Inc. Satellite TWTA on-line non-linearity measurement
US7822154B2 (en) 2001-04-27 2010-10-26 The Directv Group, Inc. Signal, interference and noise power measurement
US8005035B2 (en) 2001-04-27 2011-08-23 The Directv Group, Inc. Online output multiplexer filter measurement

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69416396D1 (en) * 1994-04-11 1999-03-18 Hewlett Packard Gmbh Noise level measurement method in the presence of a signal
ES2108620B1 (en) * 1994-12-19 1998-08-01 Instrumentacion Electronica Pr Method and apparatus for measuring the carrier to noise ratio on a televison channel.
KR100877996B1 (en) 2002-07-27 2009-01-12 엘아이지넥스원 주식회사 Method for measuring catv c/n ratio of spectrum analyzer

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4125809A (en) * 1977-11-09 1978-11-14 The United States Of America As Represented By The Secretary Of The Navy Digital C/kT meter
WO1986007157A1 (en) * 1985-05-23 1986-12-04 Comsonics, Inc. Portable spectrum analyzer
JPS61274495A (en) * 1985-05-29 1986-12-04 Nippon Hoso Kyokai <Nhk> Measuring system for cn ratio
US5313651A (en) * 1990-08-17 1994-05-17 Sony Corporation Satellite broadcast receiver

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4125809A (en) * 1977-11-09 1978-11-14 The United States Of America As Represented By The Secretary Of The Navy Digital C/kT meter
WO1986007157A1 (en) * 1985-05-23 1986-12-04 Comsonics, Inc. Portable spectrum analyzer
JPS61274495A (en) * 1985-05-29 1986-12-04 Nippon Hoso Kyokai <Nhk> Measuring system for cn ratio
US5313651A (en) * 1990-08-17 1994-05-17 Sony Corporation Satellite broadcast receiver

Non-Patent Citations (11)

* Cited by examiner, † Cited by third party
Title
"A computer-controlled satellite communications monitoring system for time division multiple access", Comsat Technical Review, Fall 1984, vol. 14, No. 2 (pp. 391-430).
"All of Spectrum Analyzer" issued May 20, 1977 by Yokogawa-Hewlett-Packard Ltd., pp. 229-231 (No translation).
"New CATV Techniques" edited by Electric Telecommunication Technology Committee, issued Nov. 20, 1987 pp. 246-257 (No translation).
"Techniques for Broadcasting Satellite" issued Nov. 20, 1982 by Nippon Hohso Publishing Kyokai, pp. 40-45 (No translation).
A computer controlled satellite communications monitoring system for time division multiple access , Comsat Technical Review, Fall 1984, vol. 14, No. 2 (pp. 391 430). *
All of Spectrum Analyzer issued May 20, 1977 by Yokogawa Hewlett Packard Ltd., pp. 229 231 (No translation). *
European Search Report, Dec. 23, 1993. *
New CATV Techniques edited by Electric Telecommunication Technology Committee, issued Nov. 20, 1987 pp. 246 257 (No translation). *
Techniques for Broadcasting Satellite issued Nov. 20, 1982 by Nippon Hohso Publishing Kyokai, pp. 40 45 (No translation). *
Test & Measurement Catalog published by Hewlett Packard Company, 1991, pp. 245, 250 252, 264, 268 269. *
Test & Measurement Catalog published by Hewlett-Packard Company, 1991, pp. 245, 250-252, 264, 268-269.

Cited By (53)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5825817A (en) * 1994-07-22 1998-10-20 Anritsu Corporation Radio wave measuring apparatus for digital communication system
US5802446A (en) * 1995-03-08 1998-09-01 U.S. Philips Corporation Method and apparatus for testing a communication channel
US5924023A (en) * 1995-12-21 1999-07-13 Anthony J. Smith Channel operation monitoring in cellular communications networks
US6021159A (en) * 1997-05-28 2000-02-01 Ikegami Tsushinki Co., Ltd. Circuit for measuring transmission quality of demodulated digital signal transmitted under carrier modulation transmission system
US6330431B1 (en) * 1997-07-08 2001-12-11 Telefonaktiebolaget Lm Ericsson (Publ) Method and apparatus for measuring signal quality in a wireless communication system
US5950110A (en) * 1997-08-06 1999-09-07 Interactive Techanologies, Inc. Jamming detection in a wireless security system
US6330432B1 (en) * 1998-02-25 2001-12-11 Nortel Networks Limited Determining SIR in a communications system
US6131014A (en) * 1998-03-17 2000-10-10 Fujitsu Limited Bidirectional communication system and upstream communication noise level determination method
WO2000019643A1 (en) * 1998-09-28 2000-04-06 Motorola Inc. A terminal unit and a method for locating a terminal unit
US6397041B1 (en) * 1999-12-22 2002-05-28 Radio Propagation Services, Inc. Broadcast monitoring and control system
US7483495B2 (en) 2001-04-27 2009-01-27 The Directv Group, Inc. Layered modulation for digital signals
US20040136469A1 (en) * 2001-04-27 2004-07-15 Weizheng Wang Optimization technique for layered modulation
US20040184521A1 (en) * 2001-04-27 2004-09-23 Chen Ernest C. Equalizers for layered modulated and other signals
US8005035B2 (en) 2001-04-27 2011-08-23 The Directv Group, Inc. Online output multiplexer filter measurement
US7920643B2 (en) 2001-04-27 2011-04-05 The Directv Group, Inc. Maximizing power and spectral efficiencies for layered and conventional modulations
US7822154B2 (en) 2001-04-27 2010-10-26 The Directv Group, Inc. Signal, interference and noise power measurement
US7778365B2 (en) 2001-04-27 2010-08-17 The Directv Group, Inc. Satellite TWTA on-line non-linearity measurement
US20060013333A1 (en) * 2001-04-27 2006-01-19 The Directv Group, Inc. Maximizing power and spectral efficiencies for layered and conventional modulations
US8259641B2 (en) 2001-04-27 2012-09-04 The Directv Group, Inc. Feeder link configurations to support layered modulation for digital signals
US7706466B2 (en) 2001-04-27 2010-04-27 The Directv Group, Inc. Lower complexity layered modulation signal processor
US7151807B2 (en) 2001-04-27 2006-12-19 The Directv Group, Inc. Fast acquisition of timing and carrier frequency from received signal
US7639759B2 (en) 2001-04-27 2009-12-29 The Directv Group, Inc. Carrier to noise ratio estimations from a received signal
US7173981B1 (en) 2001-04-27 2007-02-06 The Directv Group, Inc. Dual layer signal processing in a layered modulation digital signal system
US7184473B2 (en) 2001-04-27 2007-02-27 The Directv Group, Inc. Equalizers for layered modulated and other signals
US7184489B2 (en) 2001-04-27 2007-02-27 The Directv Group, Inc. Optimization technique for layered modulation
US7209524B2 (en) 2001-04-27 2007-04-24 The Directv Group, Inc. Layered modulation for digital signals
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US7245671B1 (en) 2001-04-27 2007-07-17 The Directv Group, Inc. Preprocessing signal layers in a layered modulation digital signal system to use legacy receivers
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US7483505B2 (en) 2001-04-27 2009-01-27 The Directv Group, Inc. Unblind equalizer architecture for digital communication systems
US7469019B2 (en) 2001-04-27 2008-12-23 The Directv Group, Inc. Optimization technique for layered modulation
US7471735B2 (en) 2001-04-27 2008-12-30 The Directv Group, Inc. Maximizing power and spectral efficiencies for layered and conventional modulations
US7512189B2 (en) 2001-04-27 2009-03-31 The Directv Group, Inc. Lower complexity layered modulation signal processor
US6985737B2 (en) * 2001-08-28 2006-01-10 Ntt Docomo, Inc. Communication channel setting method, communication controller, and radio communication system
US20060056541A1 (en) * 2002-07-01 2006-03-16 Chen Ernest C Improving hierarchical 8psk performance
US7418060B2 (en) 2002-07-01 2008-08-26 The Directv Group, Inc. Improving hierarchical 8PSK performance
US7577213B2 (en) 2002-07-01 2009-08-18 The Directv Group, Inc. Hierarchical 8PSK performance
US20040005858A1 (en) * 2002-07-03 2004-01-08 Alexandre Cervinka Detector of commercial jammer
US7738587B2 (en) 2002-07-03 2010-06-15 The Directv Group, Inc. Method and apparatus for layered modulation
US6925301B2 (en) * 2002-08-19 2005-08-02 Tektronix, Inc. Remote estimation of amplifier functionality
US20040203427A1 (en) * 2002-08-19 2004-10-14 Hill Thomas C. Remote estimation of amplifier functionality
US7474710B2 (en) 2002-10-25 2009-01-06 The Directv Group, Inc. Amplitude and phase matching for layered modulation reception
US20060153314A1 (en) * 2002-10-25 2006-07-13 Chen Ernest C Method and apparatus for tailoring carrier power requirements according to availability in layered modulation systems
US7173977B2 (en) 2002-10-25 2007-02-06 The Directv Group, Inc. Method and apparatus for tailoring carrier power requirements according to availability in layered modulation systems
US7583728B2 (en) 2002-10-25 2009-09-01 The Directv Group, Inc. Equalizers for layered modulated and other signals
US7529312B2 (en) 2002-10-25 2009-05-05 The Directv Group, Inc. Layered modulation for terrestrial ATSC applications
US7463676B2 (en) 2002-10-25 2008-12-09 The Directv Group, Inc. On-line phase noise measurement for layered modulation
US7230480B2 (en) 2002-10-25 2007-06-12 The Directv Group, Inc. Estimating the operating point on a non-linear traveling wave tube amplifier
US20050036450A1 (en) * 2003-06-16 2005-02-17 Kozue Arimori Network monitoring system, reproduction terminal, and monitoring terminal
US7502429B2 (en) 2003-10-10 2009-03-10 The Directv Group, Inc. Equalization for traveling wave tube amplifier nonlinearity measurements

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JP3135999B2 (en) 2001-02-19 grant
DE69324425T2 (en) 1999-08-05 grant
JPH06102299A (en) 1994-04-15 application
EP0588662B1 (en) 1999-04-14 grant
EP0588662A1 (en) 1994-03-23 application
KR100261831B1 (en) 2000-07-15 grant
DE69324425D1 (en) 1999-05-20 grant

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